Display device and light-emitting element

ABSTRACT

There is provided a display device including a light-emitting element body part, a low refractive index layer part which is provided over a light output surface of the light-emitting element body part and has a first refractive index, and a packaging member which is provided to seal the light-emitting element body part and the low refractive index layer part inside the packaging member, has a planar light output surface, and has a second refractive index which is greater than the first refractive index.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority to Japanese Priority PatentApplication JP 2012-205476 filed in the Japan Patent Office on Sep. 19,2012, the entire content of which is hereby incorporated by reference.

BACKGROUND

The present disclosure relates to a display device and a light-emittingelement used for the display device.

In the past, a variety of display devices using light-emitting diodes(LEDs) as light-emitting elements were proposed. In a display deviceusing LEDs (hereinafter referred to as LED displays), a plurality ofLEDs are arranged two-dimensionally.

Further, in the past, or the LED displays having such a structure, avariety of techniques were proposed so as to improve light extractionefficiency. For example, in order to improve the light extractionefficiency, a technique to seal an LED in a resin capsule formed in alens shape has been proposed (see Sheng Liu, Xiaobing Luo: “LEDPackaging for Lighting Applications: Design, Manufacturing, andTesting”, John Wiley and Sons, 2011, for example).

SUMMARY

As described above, in the past, a variety of techniques for improvingthe light-emitting efficiency were proposed for LED displays. However,in this technical field, in addition to the improvement in lightextraction efficiency, a technique that enables downsizing of LEDdisplays is also desired.

The present disclosure has been made in response to such a demand.According to an embodiment of the present disclosure, it is desirable toprovide a display device that has excellent light extraction efficiencyand enables downsizing, and a light-emitting element used for thedisplay device.

According to an embodiment of the present disclosure, there is provideda display device including a light-emitting element body part, a lowrefractive index layer part, and a packaging member, and the lowrefractive index layer part and the packaging member are configured asfollows. The low refractive index layer part is provided over a lightoutput surface of the light-emitting element body part and has a firstrefractive index. The packaging member is provided to seal thelight-emitting element body part and the low refractive index layer partinside the packaging member, has a planar light output surface, and hasa second refractive index which is greater than the first refractiveindex.

According to another embodiment of the present disclosure, there isprovided a light-emitting element including a light-emitting elementbody part and a low refractive index layer part provided over a lightoutput surface of the light-emitting element body part. Further, in thelight-emitting element of the embodiment of the present disclosure, thelow refractive index layer part has a lower refractive index than apackaging member which has a planar light output surface and with whichthe light-emitting element body part is sealed inside the packagingmember.

According to the embodiment of the present disclosure, the lowrefractive index layer part having a lower refractive index than thepackaging member having the planar light output surface is provided overthe light-emitting element body part. Accordingly, according to theembodiment of the present disclosure, it is possible to increase lightcomponents incident on the light output surface of the packaging memberfrom the light-emitting element body part at an angle smaller than thecritical angle of the total reflection of light at the light outputsurface of the packaging member.

As described above, according to the embodiment of the presentdisclosure, it is possible to increase light components incident on thelight output surface of the packaging member from the light-emittingelement body part at an angle smaller than the critical angle of thetotal reflection of light at the light output surface of the packagingmember, and accordingly, excellent light extraction efficiency can beobtained. Further, according to the embodiment of the presentdisclosure, since the packaging member having the planar light outputsurface is used, the display device can be downsized. That is, accordingto the embodiment of the present disclosure, it is possible to provide adisplay device that has excellent light extraction efficiency andenables downsizing, and a light-emitting element.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a view showing a light extraction operation in alight-emitting element (packaging mode of comparative example 1) in therelated art.

FIG. 2 is a view showing a schematic structure and a packaging mode of alight-emitting element according to a first embodiment of the presentdisclosure and a light extraction operation in the light-emittingelement.

FIGS. 3A and 3B are views showing evaluation results of light pathsimulation performed on the packaging modes of the first embodiment andthe comparative example 1.

FIGS. 4A and 4B are views showing packaging modes of comparativeexamples 2 and 3, respectively.

FIGS. 5A and 5B are views showing evaluation results of light pathsimulation performed on the packaging modes of the comparative examples2 and 3, respectively.

FIG. 6 is a view showing a relation between a thickness of a lowrefractive index layer part in the packaging mode of the firstembodiment and a luminance improvement rate.

FIG. 7 is a view showing a relation between a refractive index of thelow refractive index layer part in the packaging mode of the firstembodiment and the luminance improvement rate.

FIG. 8 is a cross-sectional view of a schematic structure of a displaydevice according to a second embodiment of the present disclosure.

FIG. 9 is a view for explaining effects (function) of a black resinlayer.

FIGS. 10A and 10B are views for explaining effects (function) of theblack resin layer.

FIG. 11 is a view showing a light extraction operation in the displaydevice of the second embodiment.

FIGS. 12A to 12C are cross-sectional views showing schematic structuresof display devices according to modified examples 1 to 3, respectively.

DETAILED DESCRIPTION

Hereinafter, examples of light-emitting elements according toembodiments of the present disclosure and display devices including anyof the light-emitting elements will be described with reference todrawings in the following order. Note that the present disclosure is notlimited to examples below.

1. First Embodiment: Structure of Light-emitting Element

2. Second Embodiment: Structure of Display Device

1. First Embodiment Structure of Light-Emitting Element

First, before a structure of a light-emitting element according to afirst embodiment is described, problems that can occur in LED displaysin the related art using LEDs when the LED displays are to be downsizedwill be specifically described.

In the LED display, in a case where each LED is sealed in a resincapsule formed in a lens shape as in a case in the related art, thetotal package of the LED tends to become large, so that the downsizingof the LED display is limited. As a measure to downsize the LED displayby solving this problem, a measure to seal the LED with a packagingmember having a planar light output surface can be considered. That is,it becomes possible to downsize the LED display by sealing the LED withthe packaging member in which the light output surface has a planarsurface, not a lens structure.

This measure, however, causes a problem in that the light extractionefficiency is decreased. Referring to FIG. 1, this problem will bespecifically described. Note that FIG. 1 is a view showing a lightextraction operation in a case (packaging mode of comparative example 1)where an LED is sealed with a resin member (packaging member) having aplanar light output surface.

Among light beams (black arrows) emitted from an LED 10, lightcomponents incident on a light output surface 20 a of a resin member 20at an angle θ1 that is greater than the critical angle (θ0 in FIG. 2described later), at which the total reflection of light occurs, can beextracted outside from the light output surface 20 a. On the other hand,light components incident on the light output surface 20 a of the resinmember 20 at an angle θ2 that is smaller than or equal to the criticalangle of the total reflection are totally reflected by the light outputsurface 20 a and fail to be extracted outside. Therefore, in a packagingmode of the LED 10 of the comparative example 1 shown in FIG. 1, thelight extraction efficiency is decreased.

Therefore, in this embodiment, a structure of a light-emitting elementby which excellent light extraction efficiency can be obtained even whenthe LED 10 is sealed with the resin member 20 having the planar lightoutput surface 20 a is proposed.

[Structure and Packaging Mode of Light-Emitting Element]

FIG. 2 is a view showing a cross-sectional structure and a packagingmode of the light-emitting element according to the first embodiment,and a light extraction operation in the light-emitting element. Notethat in a structure of a light-emitting element 1 of this embodiment anda structure of the resin member 20 (packaging member) shown in FIG. 2,structures similar to those in the comparative example 1 shown in FIG. 1are denoted by the same reference numerals.

The light-emitting element 1 includes the LED 10 (light-emitting elementbody) and a low refractive index layer part 11 provided over a lightoutput surface of the LED 10. Note that the LED 10 can be formed with agiven LED that is commercially available from the past, for example.

The low refractive index layer part 11 has a refractive index (firstrefractive index) that is smaller than a refractive index (secondrefractive index) of the resin member 20 with which the light-emittingelement 1 is sealed. Note that the low refractive index layer part 11can be formed using a given material as long as it is a material havinga refractive index that is smaller than the refractive index of theresin member 20. For example, the low refractive index layer part 11 canbe formed using SiO₂, an aerogel, or the like, or an air gap. In a casewhere the low refractive index layer part 11 is formed using SiO₂, forexample, the refractive index can be controlled by an evaporation angleof SiO₂ and a refractive index of approximately 1.08 can be obtained. Ina case where the low refractive index layer part 11 is formed using anaerogel, for example, a refractive index of approximately 1.01 can beobtained.

Further, the low refractive index layer part 11 can have a giventhickness, and for example, a thickness of approximately 1 μm can beset. Note that the refractive index and the thickness of the lowrefractive index layer part 11 can be set as appropriate according to,for example, later-described conditions such as a size of a lightextraction opening that is necessary for an LED display.

In the packaging mode of this embodiment, as shown in FIG. 2, a surface(light output surface of the light-emitting element 1) of thelight-emitting element 1 on the low refractive index layer part 11 sidehaving the above structure is sealed with the resin member 20 having theplanar light output surface 20 a.

Note that the resin member 20 can be formed using a given resin materialas long as it is a resin material having a refractive index that isgreater than the refractive index of the low refractive index layer part11. Further, as in a later-described LED display of a second embodiment,in a case where a black resin layer and a screen are provided over theresin member 20, the resin member 20 is preferably formed using amaterial that is refractive-index-matched with these constituentmembers.

[Light Extraction Operation in Light-Emitting Element]

Next, the light-extraction operation in the packaging mode of thelight-emitting element 1 of this embodiment shown in FIG. 2 will bedescribed. First, light emitted from the LED 10 is incident on the resinmember 20 through the low refractive index layer part 11. At this time,at an interface between the low refractive index layer part 11 and theresin member 20, the light travel direction is changed by a differencebetween the refractive indexes of the low refractive index layer part 11and the resin member 20. Specifically, the refractive index of the lowrefractive index layer part 11 is smaller than that of the resin member20, a light path is changed at the interface between the low refractiveindex layer part 11 and the resin member 20 to be closer to a thicknessdirection of the resin member 20 as shown in FIG. 2. That is, in thisembodiment, an angle range of light emitted from the low refractiveindex layer part 11 becomes narrower (i.e., more limited) than in a case(comparative example 1) where the low refractive index layer part 11 isnot provided.

In this case, among light beams (black arrows) emitted from the LED 10,the path of light components incident on the light output surface 20 aof the resin member 20 at an angle smaller than the critical angle θ0 ofthe total reflectance is also changed similarly at the interface betweenthe low refractive index layer part 11 and the resin member 20. As aresult, some of these light components travel through the low refractiveindex layer part 11 and then the angle of the light travel direction tothe light output surface 20 a becomes larger than the critical angle θ0of the total reflectance; therefore, the light can be extracted from thelight output surface 20 a to the outside.

That is, some of the light components that were not able to be extractedoutside in the packaging mode of the comparative example 1 shown in FIG.1 can be extracted outside by using the light-emitting element 1 of thisembodiment. This operation will be specifically described with referenceto FIGS. 3A and 3B.

FIG. 3A is a view showing a light path of light emitted from the LED 10in the packaging mode of the comparative example 1 shown in FIG. 1, thelight path being calculated by ray tracing simulation. Further, FIG. 3Bis a view showing a light path of light emitted from the light-emittingelement 1 in the packaging mode of this embodiment shown in FIG. 2, thelight path being calculated by ray tracing simulation. Note that arectangular area surrounded by a white line in FIG. 3A is an area wherethe LED 10 is disposed, and a rectangular area surrounded by a whiteline in FIG. 3B is an area where the light-emitting element 1 isdisposed.

As is clear from comparison between FIGS. 3A and 3B, in a case of usingthe light-emitting element 1 of this embodiment, a range of lightemitted from the light-emitting element 1 becomes more limited (an anglerange of emitted light becomes narrower) than in a case of thecomparative example 1. Further, as is clear from the comparison betweenFIGS. 3A and 3B, in a case of the packaging mode (light extraction mode)of the light-emitting element 1 of this embodiment, a larger amount oflight is found to be extracted outside from the light output surface 20a than in the comparative example 1. This is because, by providing thelow refractive index layer part 11 over the light output surface of theLED 10, more light components are incident on the light output surface20 a of the resin member 20 at an angle greater than the critical angleθ0 of the total reflection (light components reflected by totalreflection become less) than in the comparative example 1.

As described above, by using the light-emitting element 1 of thisembodiment, some of light components that were not able to be extractedoutside in the structure of the comparative example 1 can be extractedoutside. Therefore, in a case of using the light-emitting element 1 ofthis embodiment, the light extraction efficiency becomes higher than inthe packaging mode of the comparative example 1 (FIG. 1).

[Packaging Modes of Comparative Examples 2 and 3]

Further, the packaging mode (light extraction mode) of this embodimentwill be compared here with a packaging mode (light extraction mode) inwhich the LED 10 is sealed in a resin capsule formed in a lens form asin the above related art. FIGS. 4A and 4B show the packaging modes.

FIG. 4A is a view showing a light extraction operation in a case(packaging mode of comparative example 2) where a light-emitting elementthat is not provided with the low refractive index layer part (the LEDis provided alone) is sealed in the resin capsule formed in the lensshape. On the other hand, FIG. 4B is a view showing a light extractionoperation in a case (packaging mode of comparative example 3) where alight-emitting element provided with the low refractive index layer partis sealed in the resin capsule formed in the lens shape. Note that inthe packaging modes of the comparative examples 2 and 3 shown in FIGS.4A and 4B, respectively, structures similar to those in the packagingmode of this embodiment shown in FIG. 2 are denoted by the samereference numerals.

As is clear from comparison between FIG. 4A and FIG. 1, the packagingmode of the comparative example 2 has a structure in which a resinmember 30 having a light output surface 30 a formed in the lens shape isused as the packaging member of the LED 10 in the packaging mode of thecomparative example 1 shown in FIG. 1. Further, as is clear fromcomparison between FIG. 4B and FIG. 2, the packaging mode of thecomparative example 3 has a structure in which the resin member 30having the light output surface 30 a formed in the lens shape is used asthe packaging member of the LED 10 in the packaging mode of thisembodiment shown in FIG. 2.

Furthermore, FIGS. 5A and 5B show light paths of light emitted from theLED 10 (light-emitting element 1), the light paths being calculated byray tracing simulation in the packaging modes of the comparativeexamples 2 and 3, respectively. Note that semicircle areas surrounded bywhite lines in FIGS. 5A and 5B are areas where the resin members 30 aredisposed.

As is clear from comparison between FIGS. 5A and 5B, it is found that arange of light emitted from the light-emitting element 1 becomes morelimited and that an angle range of the output light becomes narrower inthe comparative example 3 than in the comparative example 2, because thelow refractive index layer part 11 is provided over the light outputsurface of the LED 10 in the comparative example 3.

[Evaluation of Light Extraction Efficiency]

Here, in the above-described packaging modes (light extraction modes) ofthe first embodiment and the comparative examples 1 to 3, luminances oflight output from the respective resin members are calculated bysimulation and compared. Note that in this simulation analysis, arefractive index n of the low refractive index layer part 11 is set to apredetermined value (1.10) within a range from 1.07 to 1.2, and therefractive index of the resin member is set to 1.48. Evaluation resultsare shown in the following table. Note that the luminance of outputlight in the packaging mode of the comparative example 1 (FIG. 1) is setto 1 (reference), and its relative luminances are shown in the followingtable.

Luminance First embodiment 1.29 Comparative example 1 1.00 Comparativeexample 2 2.34 Comparative example 3 1.36

As is clear from the above table, in the packaging mode of thisembodiment, the luminance is found to be increased by approximately 29%of the luminance of the packaging mode of the comparative example 1.That is, it is found that, in a case where the LED 10 (light-emittingelement 1) is packaged with the resin member 20 having the planar lightoutput surface 20 a, by providing the low refractive index layer part 11over the light output surface of the LED 10, the light extractionefficiency is improved.

Note that, as is clear from the above table, in the packaging mode ofthis embodiment, the luminance is found to be lower than in a case wherethe LED 10 (light-emitting element 1) is packaged with the resin member30 having the lens-shaped light output surface 30 a (comparativeexamples 2 and 3). However, in each of the packaging modes of thecomparative examples 2 and 3, since the resin member 30 having the lightoutput surface 30 a formed in the lens shape is used as the packagingmember, downsizing of the LED display is limited as described above. Incontrast, in this embodiment, since the light-emitting element 1 ispackaged with the resin member 20 having the planar light output surface20 a, the structure of this embodiment is superior to those of thecomparative examples 2 and 3 in terms of downsizing of the LED display.

In addition, here, relations between the thickness of the low refractiveindex layer part 11 in the packaging mode (light extraction mode) ofthis embodiment and a luminance improvement rate and between therefractive index of the low refractive index layer part 11 and theluminance improvement rate are evaluated by simulation. The evaluationresults are shown in FIG. 6 and FIG. 7.

FIG. 6 is a characteristic diagram showing the relation between thethickness of the low refractive index layer part 11 and the luminanceimprovement rate in a case where the refractive index n of the lowrefractive index layer part 11 is 1.0 (air gap) with the horizontal axisrepresenting the thickness of the low refractive index layer part 11 andthe vertical axis representing the luminance improvement rate. Further,FIG. 7 is a characteristic diagram showing the relation between therefractive index n of the low refractive index layer part 11 and theluminance improvement rate in a case where the thickness of the lowrefractive index layer part 11 is 1.0 μm with the horizontal axisrepresenting the refractive index n of the low refractive index layerpart 11 and the vertical axis representing the luminance improvementrate.

In this simulation analysis, the refractive index of a resin member is1.48, the thickness of the resin member is 17 μm, and the critical angleθ0 of the total reflection is 42°. Further, in this simulation analysis,the luminance of the packaging mode of the comparative example 1 shownin FIG. 1 is used as a reference of the luminance improvement rate.

As is clear from FIG. 6, in the evaluated range of the thickness of thelow refractive index layer part 11, it is found that the luminance(light extraction efficiency) is improved by providing the lowrefractive index layer part 11 over the LED 10. Further, as is clearfrom FIG. 7, it is found that the luminance (light extractionefficiency) is improved by lowering the refractive index n of the lowrefractive index layer part 11 to be lower than the refractive index(1.48) of the resin member.

From the above, by using the light-emitting element 1 of this embodimentas a light-emitting element of an LED display and sealing thelight-emitting element 1 with the resin member 20 having the planarlight output surface 20 a, downsizing of the LED display and theexcellent light extraction efficiency can be obtained.

2. Second Embodiment Structure of Display Device

Next, a structure example of a display device according to a secondembodiment of the present disclosure will be described. Note that in thedescription of this embodiment, an LED display is taken as an example ofthe display device.

[Structure of LED Display]

FIG. 8 shows a schematic structure of the LED display according to thesecond embodiment. FIG. 8 is a cross-sectional view of the schematicstructure of the LED display of this embodiment. Note that in an LEDdisplay 40 of this embodiment shown in FIG. 8, structures similar tothose in the packaging mode of the light-emitting element 1 of theabove-described first embodiment shown in FIG. 2 are denoted by the samereference numerals.

The LED display 40 includes the light-emitting element 1, the resinmember 20 (packaging member), a mounted substrate 41, a wiring 42, ablack resin layer 43 (light-shielding layer), and a screen 44. Further,in this embodiment, over one surface of the mounted substrate 41, thewiring 42, the light-emitting element 1, the resin member 20, the blackresin layer 43, and the screen 44 are stacked in this order. Note thatalthough FIG. 8 shows the schematic structure near one light-emittingelement 1 for simple description, actually, the LED display 40 includesa plurality of light-emitting elements 1 arranged two-dimensionally overthe mounted substrate 41.

As in the first embodiment, the light-emitting element 1 includes theLED 10 and the low refractive index layer part 11 formed over the lightoutput surface of the LED 10. Further, as in the first embodiment, theresin member 20 is formed using a sealing member (packaging member)having the planar light output surface 20 a.

Note that in this embodiment, since the screen 44 and the black resinlayer 43 are provided over the resin member 20, in order to reduce aninfluence of later-described external light reflection, the resin member20 is formed using a resin that is refractive-index-matched with thescreen 44 and the black resin layer 43. Further, also in thisembodiment, as in the first embodiment, the refractive index of the lowrefractive index layer part 11 of the light-emitting element 1 is lowerthan that of the resin member 20.

The mounted substrate 41 can be formed using a given substrate as longas it is a substrate over which the light-emitting element 1 can bemounted, such as a glass substrate, for example. The wiring 42 iselectrically connected to the LED 10 and feeds electric power to the LED10.

The black resin layer 43 is formed to be embedded in a predeterminedregion of a surface of the resin member 20 on the screen 44 side. Notethat the black resin layer 43 can be formed using a black resin materialthat is commercially available from the past.

Further, an opening 43 a (light extraction opening) is provided in aregion of the black resin layer 43 facing a light output surface 1 a ofthe light-emitting element 1 (in a region right above the light outputsurface 1 a). The size of the opening 43 a is set so that an anglebetween the light output surface 20 a and each straight line (dottedline in FIG. 8) connecting positions where end portions of the openings43 a are projected on the light output surface 44 a of the screen 44 andpositions of end portions of the light output surface 1 a of thelight-emitting element 1 is the critical angle θ0 of the totalreflection. That is, over the light output surface 1 a of thelight-emitting element 1, a conic (conical shaped) light extractionregion 40 a with a side portion having an inclination with respect tothe light output surface 20 a at the critical angle θ0 of the totalreflection is formed.

In the light-emitting element 1 of this embodiment, as described in thefirst embodiment, the low refractive index layer part 11 limits therange of light emitted from the LED 10; therefore, light can beefficiently output outside through the opening 43 a of the black resinlayer 43.

Note that in this embodiment, as shown in FIG. 8, an example in which anarea of the conic (conical shaped) light extraction region 40 a in thelight output surface 20 a of the resin member 20 is made smaller than anarea of the opening 43 a of the black resin layer 43 will be described;however, the present disclosure is not limited to this example. As longas the area of the opening 43 a is greater than or equal to the area ofthe light extraction region 40 a in the light output surface 20 a of theresin member 20, the structure (e.g., area or shape) of the opening 43 aof the black resin layer 43 can be arbitrarily set. Note that when thearea of the opening 43 a is too large, a later-described effect toreduce the influence of the external light reflection at the wiring 42is reduced. Therefore, in this embodiment, it is preferable that theopening 43 a be formed so that the area of the opening 43 a of the blackresin layer 43 is substantially equal to the area of the lightextraction region 40 a in the light output surface 20 a of the resinmember 20.

The screen 44 is formed using a material (e.g., glass) having alight-transmitting property over the resin member 20 and the black resinlayer 43.

[Function and Effects of Black Resin Layer]

Next, effects that can be obtained by providing the black resin layer 43in the LED display 40 of this embodiment will be described withreference to FIGS. 9 to 11.

Note that FIG. 9 is a cross-sectional view showing a schematic structureof an LED display (comparative example 4) in a case where alight-emitting element that does not include a low refractive indexlayer part (an LED is provided alone) is sealed with a resin memberhaving a planar light output surface. Further, FIGS. 10A and 10B arecross-sectional views of schematic structures of LED displays(comparative examples 5 and 6, respectively) each including the blackresin layer 43 in an LED display including a light-emitting element thatdoes not include the low refractive index layer part. Furthermore, FIG.11 is a view showing a light extraction operation in the LED display 40of this embodiment. Note that in each of the LED displays of thecomparative examples shown in FIG. 9 and FIGS. 10A and 10B, structuressimilar to those in the LED display 40 of this embodiment shown in FIG.8 are denoted by the same reference numerals.

An LED display 100 of the comparative example 4 has a structure inwhich, as shown in FIG. 9, the wiring 42, the LED 10, a resin member101, and the screen 44 are stacked in this order over one surface of themounted substrate 41. Further, in the LED display 100, the resin member101 is formed using a low refractive index resin material. Note that theresin member 101 may include voids.

In the structure of the LED display 100 of the comparative example 4,external light L0 incident on the LED display 100 from around the LEDdisplay 100 is reflected by the screen 44, the wiring 42, and the like(see outlined arrows L1 and L2 in FIG. 9). In this case, an influence ofthe reflected light from the screen 44 and the wiring 42 might decreasecontrast characteristics of the LED display 100. As measures to solvethis problem, the following two measures can be given.

First, as a measure to suppress the reflected light from the wiring 42,a measure to provide the black resin layer 43 over a surface of thewiring 42 can be given, as shown in the LED display 110 (comparativeexample 5) in FIG. 10A. However, it is difficult to suppress theinfluence of external light components (outline arrows L1 in FIG. 10A)reflected by the screen 44 by this measure.

As another measure to solve the above problem, a measure to form the LEDdisplay as an LED display 120 (comparative example 6) shown in FIG. 10Bcan be given. In the LED display 120 of the comparative example 6, theblack resin layer 43 is provided between the screen 44 and the resinmember 20, and the opening 43 a is provided over the LED 10, in a regioncorresponding to the light extraction region 40 a in the black resinlayer 43. Further, in the LED display 120 of the comparative example 6,the resin member 20 with which the LED 10 is sealed is formed using aresin material that is refractive-index-matched with the black resinlayer 43 and the screen 44 as in this embodiment.

In this case, the external light reflection by the screen 44 can besuppressed. Further, when seen from an incident side of the externallight L0, the wiring 42 is hidden behind the black resin layer 43 inthis structure, and accordingly, the external light reflection by thewiring 42 can also be suppressed. However, since a low refractive indexlayer part is not provided over the LED 10 in the LED display 120 of thecomparative example 6, light components incident on the screen 44 fromthe LED 10 at an angle smaller than the critical angle θ0 of the totalreflection are absorbed in the black resin layer 43, and it is difficultto extract the light components to the outside. Therefore, although theinfluence of the external light reflection (decrease in contrast) can besuppressed, the light extraction efficiency is decreased in the LEDdisplay 120 of the comparative example 6.

Unlike in the structure of the comparative examples 5 and 6, in the LEDdisplay 40 of this embodiment, the black resin layer 43 is providedbetween the screen 44 and the resin member 20; therefore, as in thecomparative example 6, the influence of the external light reflection(decrease in contrast) can be suppressed. Further, since the lowrefractive index layer part 11 is provided over the LED 10 in the LEDdisplay 40 of this embodiment, as shown in FIG. 11, light componentsincident on the screen 44 from the light-emitting element 1 at an anglesmaller than the critical angle θ0 of the total reflection can beincreased. That is, in this embodiment, most of light components emittedfrom the light-emitting element 1 are output outside through the opening43 a (conic light extraction region 40 a) of the black resin layer 43,and accordingly, the light extraction efficiency can be increased.

From the above, in this embodiment, the LED display 40 superior in bothlight extraction efficiency and contrast characteristics can beprovided. Further, in this embodiment, since the light-emitting element1 is sealed (packaged) with the resin member 20 having the planar lightoutput surface, the LED display 40 (flat panel display) with a smallfootprint can be provided.

Note that in the second embodiment, the example in which the layerformed using the black resin material is used as the light-shieldinglayer for removing the influence of the external light L0 is described,the present disclosure is not limited to this example. In the secondembodiment, a given film can be used to form the light-shielding layeras long as it is a film having the same light-shielding function as theblack resin layer 43.

Further, in the second embodiment, the structure example in which theblack resin layer 43 is provided between the screen 44 and the resinmember 20 is described, the present disclosure is not limited to thisstructure example. The black resin layer 43 can be disposed at a givenposition as long as, as in the second embodiment, the high lightextraction efficiency is maintained and more improved contrastcharacteristics of the LED display than in a case where the black resinlayer 43 is not provided is obtained. A variety of modified examples(modified examples 1 to 3) are shown in FIGS. 12A to 12C. FIGS. 12A to12C are cross-sectional views showing schematic structures of LEDdisplays of the modified examples 1 to 3, respectively. Note that in therespective LED displays of the modified examples shown in FIGS. 12A to12C, structures similar to those in the LED display 40 of the secondembodiment shown in FIG. 8 are denoted by the same reference numerals.

In an LED display 51 of the modified example 1, as shown in FIG. 12A,the black resin layer 43 is provided over the wiring 42 and in aposition that does not overlap with the region where the light-emittingelement 1 is disposed.

Further, in an LED display 52 of the modified example 2, as shown inFIG. 12B, the black resin layer 43 is provided over the light outputsurface of the screen 44. Note that in this example, as in the secondembodiment, the black resin layer 43 is formed in a region that does notoverlap with the conic (conical shaped) light extraction region 40 aformed above the light output surface 1 a of the light-emitting element1.

Furthermore, in an LED display 53 of the modified example 3, as shown inFIG. 12C, two black resin layers (first black resin layer 54 and secondblack resin layer 55) are provided. In the modified example 3, the firstblack resin layer 54 is provided to be embedded in the light outputsurface of the resin member 20 as in the second embodiment, and thesecond black resin layer 55 is provided over the wiring 42 as in themodified example 1.

Also in the LED displays of the modified examples 1 to 3, the influenceof the external light reflection by the screen 44 and/or the wiring 42can be reduced more than in a case where the black resin layer 43 is notprovided, and the contrast characteristics of the LED displays can beimproved.

Although in the second embodiment, the LED display 40 including theblack resin layer 43 and the screen 44 is described, the presentdisclosure is not limited to this example. For example, a structure inwhich the black resin layer 43 and the screen 44 are not provided andthe resin member 20 also functions as the screen is possible.

Note that in the display device (LED display) of an embodiment of thepresent disclosure, unlike in the comparative example 1, lightcomponents guided within a plane of the resin member 20 can be reducedby increasing the light extraction efficiency. Accordingly, according tothe embodiment of the present disclosure, the following effects can alsobe obtained.

Light guided within the resin member 20 is eventually absorbed in theresin member 20 and peripheral members; however, in this case, stronglight emitted from the LED 10 might degrade the resin member 20 and theperipheral members. Specifically, a sealing resin generally used in anLED display, such as an epoxy resin, an acrylic resin, or silicone, forexample, has problems on degradation, such as coloring and shrinking byabsorbing light or generation of a gas, for example.

However, in the LED display of an embodiment of the present disclosure,light components guided within the resin member 20 can be reduced asdescribed above; therefore, an influence of such a problem can besuppressed and the lifetime of the LED display can be increased.Further, in a case where the black resin layer 43 is provided as in thesecond embodiment, light components guided within the resin member 20can be further reduced. Therefore, in the embodiment of the presentdisclosure, a resin that is easily changed with light, such as a lightplastic resin or a light curable resin, can be used in a region wherethe LED 10 (light-emitting element 1) is sealed. That is, the resinmember 20 can be formed using a resin such as a light plastic resin or alight curable resin.

Further, in a display device of an embodiment of the present disclosure,a thin film transistor (TFT) for driving the LED or a circuit(light-emitting element driver circuit) such as an IC (integratedcircuit) chip can be disposed adjacent to the LED 10 (light-emittingelement 1).

In a case where such a TFT or an IC chip is provided in a region sealedwith the resin member 20, carriers excited by light emitted from the LED10 might cause malfunction of the TFT or the IC chip. However, in theLED display of the embodiment of the present disclosure, lightcomponents guided within the resin member 20 can be reduced as describedabove, and the light extraction efficiency is not decreased even whenthe black resin layer 43 is provided. Therefore, in the display deviceof the embodiment of the present disclosure, even when the TFT for LEDdriving or the IC chip is disposed adjacent to the LED 10(light-emitting element 1), stable driving is possible withoutdecreasing the luminance and a contrast ratio.

Further, the examples in which the LEDs are used as light sources aredescribed in the first and second embodiments, the present disclosure isnot limited to these examples. For example, a self-luminous light sourcesuch as organic electroluminescence (EL) or inorganic EL may also beused as the light source. Alternatively, pseudo-light source using lightpassing through a micro opening, such as a light-transmitting partincluded in each pixel of a micro electro mechanical system (MEMS)display, for example, may also be used as the light source.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

Additionally, the present application may also be configured as below.

(1) A display device including:

a light-emitting element body part;

a low refractive index layer part which is provided over a light outputsurface of the light-emitting element body part and has a firstrefractive index; and

a packaging member which is provided to seal the light-emitting elementbody part and the low refractive index layer part inside the packagingmember, has a planar light output surface, and has a second refractiveindex which is greater than the first refractive index.

(2) The display device according to (1), further including:

a light-shielding layer provided in a region which does not overlap withan extraction region of light output from the light-emitting elementbody part through the low refractive index layer part.

(3) The display device according to (2),

wherein the light-shielding layer is provided at a predeterminedposition on a light output surface side of the light-emitting elementbody part.

(4) The display device according to (2) or (3),

wherein the light-shielding layer includes a black resin.

(5) The display device according to any one of (1) to (4), furtherincluding:

a screen provided over the packaging member,

wherein the packaging member includes a member which isrefractive-index-matched with the screen.

(6) The display device according to any one of (1) to (5),

wherein the packaging member includes a resin member including any of alight plastic resin and a light curable resin.

(7) The display device according to any one of (1) to (6), furtherincluding:

a light-emitting element driver circuit which is provided in thepackaging member and drives the light-emitting element body part.

(8) A light-emitting element including:

a light-emitting element body part; and

a low refractive index layer part which is provided over a light outputsurface of the light-emitting element body part and has a lowerrefractive index than a packaging member which has a planar light outputsurface and with which the light-emitting element body part is sealedinside the packaging member.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

The invention is claimed as follows:
 1. A display device comprising: alight-emitting element body part; a low refractive index layer partwhich is provided over a light output surface of the light-emittingelement body part and has a first refractive index; and a packagingmember which is provided to seal the light-emitting element body partand the low refractive index layer part inside the packaging member, hasa planar light output surface, and has a second refractive index whichis greater than the first refractive index.
 2. The display deviceaccording to claim 1, further comprising: a light-shielding layerprovided in a region which does not overlap with an extraction region oflight output from the light-emitting element body part through the lowrefractive index layer part.
 3. The display device according to claim 2,wherein the light-shielding layer is provided at a predeterminedposition on a light output surface side of the light-emitting elementbody part.
 4. The display device according to claim 2, wherein thelight-shielding layer includes a black resin.
 5. The display deviceaccording to claim 1, further comprising: a screen provided over thepackaging member, wherein the packaging member includes a member whichis refractive-index-matched with the screen.
 6. The display deviceaccording to claim 1, wherein the packaging member includes a resinmember including any of a light plastic resin and a light curable resin.7. The display device according to claim 1, further comprising: alight-emitting element driver circuit which is provided in the packagingmember and drives the light-emitting element body part.
 8. Alight-emitting element comprising: a light-emitting element body part;and a low refractive index layer part which is provided over a lightoutput surface of the light-emitting element body part and has a lowerrefractive index than a packaging member which has a planar light outputsurface and with which the light-emitting element body part is sealedinside the packaging member.